Active matrix EL device with sealing structure housing the device

ABSTRACT

In the present invention, a semiconductor film is formed through a sputtering method, and then, the semiconductor film is crystallized. After the crystallization, a patterning step is carried out to form an active layer with a desired shape. The present invention is also characterized by forming a semiconductor film through a sputtering method, subsequently forming an insulating film. Next, the semiconductor film is crystallized through the insulating film, so that a crystalline semiconductor film is formed. According this structure, it is possible to obtain a thin film transistor with a good electronic property and a high reliability in a safe processing environment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device including asemiconductor circuit comprising a semiconductor element, such asinsulated gate type transistors, and a manufacturing method thereof. Inparticular, it relates to the technology for forming crystallinesemiconductor films on top of insulating surfaces. The semiconductordevice of the present invention is not limited to thin film transistors(TFTs), MOS transistor, and other insulated type gate transistorelements themselves, but instead include display devices, image sensors,and other electro-optical devices incorporating semiconductor circuitsmade from those insulated gate type transistors. In addition, thesemiconductor device in the present invention includes electronicequipment incorporating the display devices or electro-optical devices.

2. Description of the Related Art

Active matrix liquid crystal displays, in which a pixel matrix circuitand a drive circuit are comprised of thin film transistors (TFTs) formedon top of a substrate with insulating properties, continue to be acenter of attention. Liquid crystal displays from approximately 0.5 to20 inches in size are in use.

Currently TFTs which have a crystalline semiconductor film as the activelayer, such as the representative polysilicon film, are gatheringattention in the drive to make a liquid crystal display that is capableof high definition display.

A crystalline semiconductor film is formed by initially forming anamorphous semiconductor film, such as the representative amorphoussilicon film, and then crystallizing it. In general, chemical vapordeposition (CVD) is used to form the amorphous semiconductor film.

Until now, the low pressure CVD method, which can deposit a good qualityamorphous silicon film, as well as the plasma CVD method, which has goodthroughput and deposits an amorphous silicon film at low temperature,have often been employed.

The speed that reduced pressure CVD can form an amorphous semiconductorfilm is slow, a disadvantage from a manufacturing perspective.

In addition, plasma CVD forms an amorphous semiconductor film bydecomposition of a high priced reactive gas (monosilane, disilane, etc.)using sufficient RF power, but at that time, in addition to theamorphous semiconductor film, a large amount of a yellow powder isgenerated through a polymerization reaction. This powder is ultrafine,and is known to cause powder explosions when exposed to the atmosphere.

Therefore, due to the great danger of an explosion, a process that usesplasma CVD has a disadvantage from a workplace safety perspective.

Additionally, in the past, after the formation of the amorphoussemiconductor film, several other processes are carried out (forexample, crystallization, patterning) before the gate insulating film isactually formed. This means the surface of the crystallized siliconfilm, which is to become the active layer, is exposed to the atmosphereand may become either contaminated with impurities (oxygen, moisture,boron, sodium) or oxidized before the gate insulating film can beformed. Then when the gate insulating film is laminated on top, theactive layer, especially the interface between the channel formationregion and the gate insulating film, properties drop, and this causes adrop in the electrical characteristics of the TFT.

This is especially true for the atmosphere in clean rooms, in whichboron (boric) from the HEPA type filter generally in use can cause boronto intermix with the exposed surface of the film in unevenconcentrations. To make a glass mesh structure for the HEPA filter withease, glass contains a high level of boron. In addition, after measuringthe electrical characteristics of the TFT, it has been found that theboron inhibits crystallization during the semiconductor filmcrystallization process.

SUMMARY OF THE INVENTION

In accordance with the background described above, an object of thepresent invention is to provide a process that can deposit a film at lowtemperature, and by forming an amorphous semiconductor film usingsputtering method of superior productivity, and that has a high level ofsafety.

In addition, an object of the present invention is to provide asemiconductor device, which includes a semiconductor circuit made from asemiconductor element with high quality electrical characteristics. Thehigh quality electrical characteristics result by using sputtering toform an amorphous semiconductor film and then crystallizing the film,with the resulting crystalline semiconductor film as the active layerforming a good interface with the insulating film.

In order to obtain the above objects, the present invention ischaracterized by using sputtering to form a semiconductor film, thencrystallizing the film, resulting in formation of a crystallinesemiconductor film. It is also characterized by using sputtering to forma base film as well as a gate insulating film.

In addition, the present invention is characterized by using sputteringto form a semiconductor film, and then after successive formation of aninsulating film, performing crystallization through the insulating film,resulting in the formation of a crystalline semiconductor film.

This type of composition realizes a TFT with good electricalcharacteristics through use of a process that provides a safe workenvironment.

A first aspect of the present invention is a semiconductor device whichincludes a semiconductor circuit made from a semiconductor elementhaving an active layer and an insulating film in contact with the activelayer on the surface of an insulator, the element characterized in thatthe active layer is a semiconductor film formed by sputtering andcrystallized while in contact with the insulating film.

In the first aspect of the present invention, the element ischaracterized in that the sputtering method uses as a target eithersilicon, or a material with silicon as its major component, to form asemiconductor film through RF power.

In addition, in the first aspect, the element is characterized in thatthe insulating film is formed by the sputtering method.

Further, the element is characterized in that the insulating film iseither a single layer film or a laminated film of silicon nitride,oxidized silicon nitride, or silicon oxide.

A second aspect of the present invention is a semiconductor device whichincludes a semiconductor circuit made from a semiconductor elementcomprising an active layer formed by sputtering on the surface of aninsulator, a gate insulating film in contact with the active layer, andgate wiring in contact with the gate insulating film, the elementcharacterized in that the active layer has at least a channel formationregion, with a source region and drain region formed on both sides ofthe channel formation region.

A third aspect of the present invention is a semiconductor device whichincludes a semiconductor circuit made from a semiconductor elementhaving gate wiring on the surface of an insulator, a gate insulatingfilm in contact with the gate wiring, and an active layer, formed bysputtering, in contact with the gate insulating film, the elementcharacterized in that the active layer has at least a channel formationregion, with a source region and drain region formed on both sides ofthe channel formation region.

Additionally, the second aspect and the third aspect of the presentinvention are both characterized in that at least the source region andthe drain region include a catalytic element that promotes thecrystallization of silicon.

Further, the above aspects are characterized in that the catalyticelement includes one element, or plurality of elements selected from agroup consisting of Ni, Fe, Co, Pt, Cu, Au, Ge, and Pb.

Note that the term amorphous semiconductor film is used throughout thespecification to refer to a semiconductor film including amorphousmaterials. For example, an amorphous semiconductor film withmicro-crystals such as a Si film, a Ge film, or a compound semiconductorfilm (for example, an amorphous silicon germanium film expressed asSi_(x)Ge_(1-x) where 0<x<1).

Further note that the term crystalline semiconductor film is usedthroughout the specification to refer to either a single crystalsemiconductor film, or to a semiconductor film that includes grainboundaries (a polycrystalline semiconductor film or a micro-crystallinesemiconductor film), and is clearly differentiated from an amorphoussemiconductor film in that the latter has a non-crystalline state overthe entire film area. Of course, when only semiconductor film is usedthroughout the specification, the term refers to crystallinesemiconductor films as well as non-crystalline semiconductor films.

In addition, the term semiconductor element is used throughout thespecification to refer to switching elements and memory elements, forexample thin film transistors (TFT) and thin film diodes (TFD).

A first aspect of the manufacturing method of the present invention is amethod for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of forming a semiconductor film bysputtering on top of the surface of an insulator, and forming acrystalline semiconductor film by crystallizing the sputteredsemiconductor film.

A second aspect of the manufacturing method of the present invention isa method for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of forming a semiconductor film bysputtering on top of the surface of an insulator, adding catalyticelements into at least a portion of the semiconductor film to promotecrystallization, and forming a crystalline semiconductor film bycrystallizing the semiconductor film.

A third aspect of the manufacturing method of the present invention is amethod for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of forming a semiconductor film bysputtering on top of the surface of an insulator, adding catalyticelements into at least a portion of the semiconductor film to promotecrystallization, forming a crystalline semiconductor film bycrystallizing the semiconductor film, and reducing the concentration ofthe catalytic elements throughout the crystalline semiconductor film.

A fourth aspect of the manufacturing method of the present invention isa method for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of forming a semiconductor film bysputtering on top of the surface of an insulator, forming an insulatingfilm in contact with the semiconductor film, and forming a crystallinesemiconductor film by crystallizing the semiconductor film while it isin contact with the insulating film.

A fifth aspect of the manufacturing method of the present invention is amethod for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of doping catalytic elements overat least a portion of the surface of an insulator to promotecrystallization, forming a semiconductor film by sputtering, forming aninsulating film in contact with the semiconductor film, and forming acrystalline semiconductor film by crystallizing the semiconductor filmwhile it is in contact with the insulating film.

A sixth aspect of the manufacturing method of the present invention is amethod for manufacturing a semiconductor device which includes asemiconductor circuit made from a semiconductor element, and ischaracterized by comprising the steps of adding catalytic elements intoat least a portion of the surface of an insulator to promotecrystallization, forming a semiconductor film by sputtering, forming aninsulating film in contact with the semiconductor film, forming acrystalline semiconductor film by crystallizing the semiconductor filmwhile it is contact with the insulating film, and reducing theconcentration of the catalytic elements throughout the crystallinesemiconductor film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing an example of the structure according toEmbodiment 1 of the present invention;

FIGS. 2A, 2B, and 2C are drawings showing an example of a manufacturingprocess according to Embodiment 1 of the present invention;

FIGS. 3A, 3B, and 3C are drawings showing an example of themanufacturing process according to Embodiment 1 of the presentinvention;

FIGS. 4A, 4B, and 4C are drawings showing an example of themanufacturing process according to Embodiment 1 of the presentinvention;

FIGS. 5A and 5B are drawings showing an example of the manufacturingprocess according to Embodiment 1 of the present invention;

FIGS. 6A and 6B are drawings showing top views of the structureaccording to Embodiment 1 of the present invention;

FIGS. 7A to 7G are drawings showing an example of a manufacturingprocess according to Embodiment 4 of the present invention;

FIG. 8 shows an active matrix display device in Embodiment 5 of thepresent invention;

FIG. 9 is a drawing showing an example of the structure according toEmbodiment 6 of the present invention;

FIGS. 10A to 10D are drawings showing an example of a manufacturingprocess according to Embodiment 6 of the present invention;

FIGS. 11A, 11B, and 11C are drawings showing an example of themanufacturing process according to Embodiment 6 of the presentinvention;

FIGS. 12A, 12B, and 12C are drawings showing an example of themanufacturing process according to Embodiment 6 of the presentinvention;

FIGS. 13A and 13B are drawings showing the example manufacturing processfor Embodiment 6 of the present invention;

FIGS. 14A and 14B are drawings showing top views of the structureaccording to Embodiment 6 of the present invention;

FIGS. 15A to 15D are drawings showing an example of a manufacturingprocess according to Embodiment 10 of the present invention;

FIGS. 16A, 16B, and 16C are drawings showing an example of themanufacturing process according to Embodiment 10 of the presentinvention;

FIGS. 17A and 17B are drawings showing an example of a device accordingto Embodiment 9 of the present invention;

FIGS. 18A to 18H are drawings showing an example of electronicequipments according to Embodiment 12 of the present invention;

FIGS. 19A to 19D are drawings showing an example of electronicequipments according to Embodiment 13 of the present invention; and

FIGS. 20A and 20B are drawings showing an example of anelectroluminescence display device to Embodiment 14 of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to FIGS. 2A to 2C.

First, a substrate 100 is prepared. Glass, quartz, crystallized glassand other insulators, ceramics, stainless steel and other metals(tantalum, tungsten, molybdenum, etc.), semiconductors, plastics(polyethylene-terephthalate), etc., can be used as the substrate 100.

Next, an insulating base film 101 (referred to as base film throughoutthe rest of the specification) is formed on top of the substrate 100.Silicon oxide, silicon nitride, silicon nitride oxide (SiO_(x)N_(y)), ora laminate of more than one may be used as the base film 101, with athickness in the range 100 to 500 nm. Sputtering is a recommended meansfor forming the base film due to its good safety and productivity.However, other methods such as thermal CVD, plasma CVD, evaporation, lowpressure thermal CVD, etc. may also be employed. The base film has theeffect of preventing diffusion of impurities from the substrate. Notethat the base film is only intended to improve the electricalcharacteristics of the TFT, and need not be included.

Next, a semiconductor film 102 is formed on top of the base film 101 bysputtering, as shown in FIG. 2A. The semiconductor film 102 can be afilm made from amorphous silicon, an amorphous semiconductor containingmicro-crystals, a micro-crystalline semiconductor, amorphous germanium,amorphous silicon germanium of the form Si_(x)Ge_(1-x), where 0<x<1, orfrom a laminate of more than one of the above, with a thickness in therange of 20 to 70 nm (typically 40 to 50 nm).

The sputtering apparatus used in the embodiments of the presentinvention basically consists of chambers, an evacuation system forcreating a vacuum in the chambers, a gas input system for introducingthe gas used during sputtering to the chambers, an electrode system withtargets, RF electrodes, etc., and a sputtering power source connected tothe electrode system.

Silicon, or a material with silicon as its major component, is used as atarget. In addition, it is desirable that the target be stronglyorientated to a surface providing a crystal face orientation of thesilicon film ((100), (111), (110), etc.) A thin film with almost thesame composition as the target is formed when sputtering, so sputteringhas the merit of allowing one to be able to form a thin film withdesired composition by regulating the composition of the target. Inaddition, the film growth rate is almost proportional to the sputteringvoltage, and is stable.

Further, inert element gasses such as Ar, He, Ne, N, etc. are usedeither singly or in combination as the sputtering gas. In addition,hydrogen gas, etc., may be added in order to regulate the hydrogenconcentration in the semiconductor film.

Note that in the present invention, the semiconductor film 102 is formedby evacuating the sputtering chamber to form a high vacuum (equal to orless than 1×10⁻⁴ Pa), introducing the sputtering gas into the chamber,setting the deposition pressure to between 0.2 and 0.6 Pa, setting thetemperature of the substrate to between 100 and 400° C., and setting theRF power to between 200 and 2500 W (per unit target area, between 1 and15 W/cm²). Also note that the sputtering conditions (sputtering gas, gasflow rate, deposition pressure, substrate temperature, deposition power,etc.) may be determined by considering the size of the target, thedimensions of the substrate, the film thickness of the semiconductorfilm, the quality of the semiconductor film, etc.) In addition, a powersupply with a frequency of 13.56 MHZ and an impedance of 50 Ω isgenerally used, but if its frequency is high enough to generate aplasma, there are no specific limitations on the voltage supplyspecifications. It is also possible to substitute a DC power for the RFpower.

In the sputtering method, the ions inside a plasma are accelerated,causing a sputter when the ions impact the target. The atoms that aredislodged from the target by the ion impacts then adhere to thesubstrate, forming a thin film. The chief way to perform sputtering isby using a target that includes as the constituent elements the atomsthat need to be included in the film to be formed (co-sputteringmethod), but other methods exist, such as reactive sputtering in which areactive gas (for example, oxygen, ammonia, etc.) is introduced duringthe process of sputtering the target.

Note that it is desirable that a cleaning process, such as plasmaetching, be carried out on the surface of the substrate before forming afilm using sputtering.

In addition, the base film and the semiconductor film may be formed insuccession, without exposing the substrate and films to the atmosphere.A film deposition apparatus is shown in FIGS. 17A and 17B, and may beused to form films in succession.

The multi-chamber film deposition apparatus shown in FIGS. 17A and 17Bis an example of a sputtering apparatus in which each of the reactionchambers (chambers) is provided with a target of differing composition(or of different elements), allowing a multiple number of films withdiffering composition to be-laminated in succession.

An explanation of the simple structure of the sputtering apparatus shownin FIGS. 17A and 17B follows here. FIG. 17B is a schematic diagram ofthe cross-section of the apparatus shown in FIG. 17A, along the dashedline. FIG. 17A shows three chambers, but the actual number of chambersemployed may be increased or decreased depending on the requirements ofthe work to be performed. A substrate 10 to be processed, a commonchamber 11, a conveyer mechanism 12 for conveying the substrate 10 to beprocessed from one location to another, a target support platform 31, ashutter 33, and a substrate holder 34 are shown. The substrate is takeninto and brought out from load lock chambers 13 and 14 fixed to the mainbody of the apparatus. Note that substrate conveyor cassettes 15 and 16are set, respectively, in the load lock chambers 13 and 14. In addition,gate valves 17 and 18 allow an airtight seal to be made between the loadlock chambers 13 and 14, and the common chamber 11. Further, chambers19, 20, and 21 are connected to the common chamber 11, and gate valves22, 23, and 24 are connected to each chamber, respectively, in order toform an airtight seal with the common chamber. Chambers 19, 20, and 21are each outfitted with a low pressure vacuum pump that is capable ofproducing an extremely high vacuum (1×10⁻⁸ torr or less, preferably1×10⁻⁹ torr or less). By using this type of apparatus, it is possible tosuccessively form films by lamination without exposure to theatmosphere.

Successive formation of films in the present specification indicatesthat films are formed one after another while at high vacuum, withoutexposure to the atmosphere. For example, this may be accomplished bymoving the substrate between different chambers while remaining under ahigh vacuum, or successive films may be formed inside one chamber, allthe while under high vacuum, with no exposure to the atmosphere ineither case.

Using this type of process leads to a clean interface between the basefilm and the semiconductor film.

Compared to the plasma CVD process that has been used in the past, withthe sputtering method of the present invention, described above, theadhesion to the base film and the substrate is high, and a semiconductorfilm with a desired film quality (density of hydrogen, oxygen, and otherimpurities in the film) can be formed.

Next the semiconductor film 102 is put through a crystallizationprocess, resulting in a crystallized semiconductor 103, as shown in FIG.2B.

The film obtained using the sputtering method of the present inventionis a starting point, and the film that is then obtained after thecrystallization process differs from previous crystalline semiconductorfilms. The current invention produces a crystalline semiconductor filmin which a columnar structure can be observed The crystallizationprocess in the present invention can be accomplished by using any ofseveral well-known means. For example, crystallization by eitherinfrared or ultraviolet irradiation (laser crystallization), lasercrystallization using a catalytic element, thermal crystallization,thermal crystallization using a catalytic element, etc. are allprocesses that may be used either singly or in combination.

The stresses induced on the substrate are especially small with lasercrystallization, and the process can be carried out in a short amount oftime, making it an effective process. For ultraviolet lasercrystallization, either an excimer laser beam or the strong light raysemitted by an ultraviolet lamp may be employed. Infrared lightcrystallization may be performed similarly using either an infraredlaser beam, or the strong light rays emitted by an infrared lamp. Notethat pulse lasers using XeCl, ArF, KrF, and other gasses, orcontinuous-wave lasers such as Ar laser can be employed, with a linearshaped laser beam (several millimeters by several centimeters), or alaser beam either rectangular or square.

Note that the specific conditions used during laser crystallization(laser beam shape, laser wavelength, overlap ratio, irradiationstrength, pulse width, repeating frequency, irradiation time, etc.) canbe set by the operator depending on the thickness of the semiconductorfilm, the substrate temperature, etc. Further, depending upon theconditions selected for the laser crystallization process, thesemiconductor film may pass into a melted state before crystallization,or may remain in a solid state, or pass into an intermediate statebetween the solid and liquid states to be crystallized. However, if thelaser crystallization is carried out under exposure to the atmosphere, athin oxide layer is formed and there are cases in which it should beremoved in a later process. It is also possible to perform the lasercrystallization process on the semiconductor film inside the samechamber in which the sputtering process takes place, without allexposure to the atmosphere.

A thermal crystallization process which uses a doped catalytic element(nickel) to promote crystallization is discussed in detail in JapanesePatent Application Laid-open No. Hei 7-130652 and in Japanese PatentApplication Laid-open No. Hei 9-312260. Metal elements that promotecrystallization include Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au,which may be used either singly or in combination. In addition,substitution diffused Ge and Pb that are diffused throughout theamorphous silicon film may also be used.

However, laser crystallization processes and thermal crystallizationprocesses that employ a catalytic element leave a high concentration ofthe catalyst remaining within the semiconductor film, so a reductionprocess such as gettering should be used after crystallization to reducethe catalytic element concentration in the semiconductor film.

Next, the crystallized semiconductor film 103 is patterned, forming anactive layer 104 into a desired shape, as shown in FIG. 2C. The activelayer 104 is then covered by forming an insulating film 105 (which willbecome a gate insulating film after further processing).

A silicon oxide film, silicon nitride film, silicon nitride oxide(SiO_(x)N_(y)) film, or an organic resin film such as benzocyclobutene(BCB) film may be used either singly or in a laminate of more than oneas the insulating film 105. Well-known processes such as thermal CVD,plasma CVD, low pressure thermal CVD, sputtering, evaporation, andcoating may be used as the means to form the insulating film, whichshould have a film thickness in the range of 10 to 300 nm.

In the scope of the present invention, the sputtering method isdesirable to form the semiconductor film 102 and the insulating film105, based on a safe work environment. A silicon oxide target, or atarget that is comprised of a material with silicon oxide as its primarycomponent, is used in the sputtering method. Also, inert gasses such asAr, He, Ne, N, etc. are used either singly or in a combination of morethan one as the sputtering gas. In addition, it is desirable to addgaseous oxygen to control the quality of the film. The specificsputtering conditions (sputtering gas, gas flow rate, depositionpressure, substrate temperature, power strength, etc.) may be set by theoperator after taking into consideration the size of the target, thedimensions of the substrate, the film thickness of the insulating film105, the quality of the insulating film 105, etc.

Note that the order of the manufacturing processes described above maybe set by the operator depending on the type of elements to bemanufactured. For example, to manufacture a bottom gate TFT, aftermaking the base film the gate wiring is formed, next the insulating film(gate insulating film) is formed, and then the semiconductor film of thepresent invention (by sputtering) is laminated on top. In addition, aprocess where the crystalline semiconductor film 103 is formed, then theinsulating film 105 is laminated, and the patterning of the crystallinesemiconductor film 103 occurs after the formation of the insulating film105, may be employed.

It is possible to apply the active layer 104 or the insulating film 105,formed by the above manufacturing methods, to more than just simpleelements like thin film transistors (TFTs) and MOS transistors. It canbe applied also to semiconductor devices such as display devices andimage sensors, etc., which contain semiconductor circuits comprised ofthese insulated gate transistors.

Instead of the process described above, it is also possible to take aprocess of forming a semiconductor film 1150 by the sputtering method,then forming an insulating film 1151, successively, followed bycrystallizing the semiconductor film through the insulating film. Thisgives a crystalline semiconductor film 1152, as in the example shown inFIGS. 10A to 13B. The deposition apparatus shown in FIG. 17A and 17B maybe used for the successive formation of the insulating film 1151. Theapparatus may also be used to form the semiconductor film 1150 bysputtering, to form the insulating layer 1151 by sputtering, and toperform laser crystallization on the semiconductor film 1150, all withinthe same chamber, without exposure to the atmosphere. In addition, asilicon oxide film, silicon nitride film, or silicon nitride oxide(SiO_(x)N_(y)) film, either singly or in a laminate of more than one,may be used as the insulating film 1151. Well-known processes such asthermal CVD, plasma CVD, low pressure thermal CVD, sputtering andevaporation can be used to form the insulating film 1151, with a filmthickness in the area of 1 to 50 nm. Thus, by successively forming theinsulating film 1151 after forming the semiconductor film 1150, withoutexposure to the atmosphere, good interface characteristics between filmscan be obtained.

Instead of the above process, it is possible to take a process where aninsulating film is formed on top of a crystalline semiconductor film,where the crystalline semiconductor film undergoes patterning afterformation of the insulating film.

The following description of preferred embodiments is given forillustrative purposes only and is not to be construed as imposing anylimitations on the scope of the present invention.

Embodiment 1

In this embodiment, a description will be made on an example in which aCMOS circuit, that is a part of a peripheral drive circuit, and a pixelTFT, that is a part of a pixel matrix circuit, are formed on the singlesame substrate using the present invention. The semiconductor device andits manufacturing method will be described briefly with reference to thesimple cross sectional drawings shown in FIGS. 1 to 6B.

First the substrate 100 is prepared. In this embodiment, a glasssubstrate (Corning 1737, distortion point 667° C.) is used. Next, aftera base insulating film (hereinafter in this specification, referred toas base film) is formed on top of the substrate 100, it is annealed. Theheat treatment here is performed below the distortion point of thesubstrate, preferably between 200 and 700° C. In Embodiment 1, TEOS andoxygen (O₂) are used as raw material gasses in a plasma CVD apparatus inorder to form a 200 nm thick silicon oxide film as the base film 101,which is then annealed at 640° C. for 4 hours.

The semiconductor film 102 is then formed on top of the base film 101 bysputtering, as FIG. 2A shows. Silicon is used as the target (6 φ) and Argas (gas flow rate 20 to 50 sccm) is used as the sputtering gas forEmbodiment 1. In addition, either hydrogen gas or helium gas may beadded (gas flow rate 1 to 50 sccm) to regulate the hydrogen density inthe semiconductor film.

After the state shown in FIG. 2A is reached, crystallization of thesemiconductor film 102 is performed, forming the crystallinesemiconductor film 103, a crystalline silicon film. Lasercrystallization of the semiconductor film 102 is employed inEmbodiment 1. In this embodiment, XeCl excimer laser light is formedinto a linear (0.4 mm×length 135 mm) beam and irradiated, underatmospheric conditions (FIG. 2B). The laser beam has a 30 Hz pulsefrequency, an overlap ratio of 96%, and a laser energy density of 359mJ/cm². Note that due to the laser being used in the atmosphere, a thinoxidation layer is formed on the surface, but it is not shown in FIG. 2Bin order to simplify the explanation of Embodiment 1.

After the processing in FIG. 2B is completed, it is acceptable to addimpurities in order to control the threshold value, and it is alsoacceptable to add impurities in a region to be the channel formationregion.

The crystalline semiconductor film 103 is patterned next, forming theactive layer 104 in a desired shape. The active layer 104 is thencovered by forming the insulating film 105 (which will become a gateinsulating film after further processing), a silicon oxide film 150 nmin thickness deposited by sputtering (FIG. 2C).

A conductive film (material layer for gate wiring) is then formed on topof the insulating film 105.

Further, either conductor or semiconductor materials may be used for theconductive film. For example, usable as the conductive film is a singlelayer containing as the main constituent aluminum (Al), tantalum (Ta),copper (Cu), niobium (Nb), hafnium (Hf), zirconium (Zr), titanium (Ti),chromium (Cr), silicon (Si) or silicide, or multi-layers thereof. A filmthickness of 10 to 500 nm can be used for the conductive film. A 400 nmaluminum film is deposited as the conductive film for Embodiment 1.

The conductive film is then patterned using a mask 107, and the materiallayer 106 that will form the gate wiring is formed, as shown in FIG. 3A.

A first anodic oxidation is performed on the material layer 106 thatwill form the gate wiring, forming an anodic oxidation film 108 that isporous, as shown in FIG. 3B. Additionally, after removal of the mask107, a second anodic oxidation is performed, forming a fine anodicoxidation film 109, and then forming a gate wiring 110, as shown in FIG.3C. Next, the gate wiring 110, and anodic oxidation films 108 and 109are used as a mask to pattern the insulating film 105, forming a gateinsulating layer 111, as shown in FIG. 4A. The porous anodic oxidationfilm 108 is then removed, as shown in FIG. 4B. Alternatively, aninsulating film covering the gate wiring, which is a protective film toprotect the gate wiring, may be formed without performing the anodicoxidation above.

The insulating film 105 may not be patterned in FIG. 4A, but it may bepatterned after adding impurities in the active layer through theinsulating film 105.

Next, the n-channel TFT is covered with a mask 201, and impurities aredoped in the active layer 104 to give it p-type conductivity using as amask the gate wiring 110. In addition, it is possible to form a maskthat will allow for the selective adding of impurities to a preset areaof the active layer 104. Ion implantation, plasma doping, laser doping,and other well-known methods may be used as a means for addingimpurities. However, the dose, the acceleration voltage, and otherdoping conditions are regulated in order to ensure that the impuritiesare doped to specific locations of the active layer in the presetamount. Boron is used as an impurity to provide p-type conductivity inEmbodiment 1. After the impurity adding process described above iscarried out, heavy impurity regions (p⁺-type regions) 112 and 113 act assource and drain regions, while light impurity regions (p⁻-type regions)114 and 115 act as LDD regions. The region 116 that serves as anintrinsic, or essentially intrinsic, channel formation region is alsoshown in FIG. 4C. The mask 201 is then removed.

Next, the p-channel TFT is covered with a mask 202, and impurities areadded to the active layer to impart n-type conductivity. Phosphorous isused as an impurity to provide n-type conductivity in Embodiment 1.After the impurity adding process described above is carried out, heavyimpurity regions (n⁺-type regions) 117 and 118 act as source and drainregions, while those light impurity regions (n⁻-type regions) 119 and120 act as LDD regions. Further, regions not implanted with eitherphosphorous or boron ions become an intrinsic, or essentially intrinsic,channel formation region 121, used to route the carrier, as shown inFIG. 5A. Thereafter, the mask 22 is removed.

Note that the term intrinsic is used throughout the specification torefer to a region in which no impurities is included to change the Fermilevel of silicon. In addition, the term essentially intrinsic is used torefer to a region in which the number of electrons and poles isperfectly balanced, a region that counteracts conductivity. In otherwords, essentially intrinsic refers to a region containing impurities,that give either a p-type or n-type conductivity, with a controllablethreshold value range of concentration (1×10¹⁵ to 1×10¹⁷ atoms/cm³ whenanalyzed by SIMS). Or it refers to a region in which impurities thatexhibit reverse conductivity are intentionally added in order tocounteract the conductivity.

Next, a well-known process such as thermal annealing or laser annealingis carried out in order to obtain an activation effect of the impuritiesin the source and drain regions, and to get a restorative effect for anydamage to the active layer crystal structure that was caused during thedoping process. In Embodiment 1, after irradiation by laser light with apulse frequency of 50 Hz, and a laser energy density of 179 mJ/cm²,thermal activation is performed (in a nitrogen atmosphere, 405° C., 2hours.)

Afterward, it is also acceptable to form a passivation film by coveringwith oxidized silicon nitride film, silicon nitride film, etc., in orderto protect the work.

Next, as shown in FIG. 5B, a first interlayer insulating film 122, asilicon nitride oxide film (SiO_(x)N_(y)) in the Embodiment, is formed,and then after contact holes are formed to expose the source and drainregions, a metallic film is formed. This is patterned, forming metallicwirings 123 to 127 that provide contact with the source and drainregions. Finally, a hydrogenation process is performed (hydrogenatmosphere, 350° C., 2 hours.)

The n-channel TFT and p-channel TFT are manufactured by performing theseprocesses.

Next, a second interlayer insulating film 128 is formed by spin coatingan acrylic resin film to a thickness of 1 μm. The second interlayerinsulating film 128 is then etched, and after contact holes are formed,a 300 nm Ti metallic film is deposited. After then patterning themetallic film, a black mask 131 and lead wires 129 and 130 are formed.

Further, a third interlayer insulating film 132 is formed by an acrylicresin. In Embodiment 1 the third interlayer insulating film 132 isformed by spin coating to a thickness of 1 μm.

A contact hole is then formed, and a pixel electrode 133 is formed. InEmbodiment 1, first a transparent conductive film, for example, an ITOfilm is sputtered to a thickness of 100 nm, and then it is patterned,forming the pixel electrode 133. As a pixel electrode, a compoundcomprising indium oxide and zinc oxide can be also employed instead ofITO. Finally, this is treated with heat for 1 hour at 350° C. in ahydrogen atmosphere, reducing defects throughout the semiconductorlayers. The conditions shown in FIG. 1 are thus obtained.

Although used for the explanation in FIG. 1 is a double gate structurepixel matrix TFT, the present invention may also be applied to singlegate, triple gate, and other multiple gate structures.

FIGS. 6A and 6B are equivalent to top views of the drawing shown inFIG. 1. The dotted line X-X′ represents the cross sectional view of thepixel matrix circuit construction in FIG. 1, while the dotted line Y-Y′represents the cross sectional view of the CMOS circuit construction inFIG. 1. An active layer 310, a scanning line 320, a gate wiring 320E, asignal line 331, a drain electrode 332, a black mask 341, and a pixelelectrode 350 are all shown in FIG. 6A. In FIG. 6B, active layers 410and 420, gate wirings 425 and 430, source electrodes 441 and 442, adrain electrode 443, a drain wiring 451, and a source wiring 452 areshown.

The TFT structure shown in Embodiment 1 is an example of a top gatetype, and places no special limitations on the structure ofEmbodiment 1. In addition, Embodiment 1 shows the manufacture of atransmissive LCD, which is just one example of a semiconductor device.Note that by suitably constructing the pixel electrode from a highlyreflective metal film, instead of ITO, and then changing the patterningof the pixel electrode, the operator can easily manufacture a reflectiveLCD. In addition, by using as a base film a structure consisting of aheat resistant metal film and an insulating film layered thereon, or astructure consisting of an insulating film formed on top of aluminumnitride during manufacture of the reflective LCD, the metallic filmunderneath the insulating film will work effectively as a heat radiationlayer. Also note that operators may suitably change the order of theabove processes as needed.

Embodiment 2

This embodiment takes an example in which a process that differs fromthat of Embodiment 1 is used to obtain a crystalline semiconductor film.In Embodiment 2 an additional process is performed before or afterformation of the semiconductor film of Embodiment 1, which places acatalytic element either selectively or over the entire semiconductorsurface, in order to promote crystallization. The basic structure ofEmbodiment 2 is similar to that of Embodiment 1, therefore the focus ofthe description will be on the differences only.

Embodiment 2 is the same as Embodiment 1 through the process of formingthe semiconductor film by sputtering.

A catalytic element to promote silicon crystallization is introducedinto the semiconductor film surface in Embodiment 2. Elements Ni, Fe,Co, Pt, Cu, Au, and Ge may be used either singly, or in combination, asthe catalyst for promoting silicon crystallization. Ni was chosen forEmbodiment 2 due to its quick diffusion speed throughout the amorphoussilicon film, and the extremely good quality crystal obtained.

In addition, there are no special limitations on what location the abovecatalytic element may be introduced. It is added either over the entireamorphous silicon surface, or added to selective areas through use of asuitable mask. In addition, the catalytic element may be introduced onthe bottom surface of the amorphous silicon film, or even on both thebottom and top surfaces.

Further, there are no special limitations on what type of processingmethod is used to introduce the catalytic element to the amorphoussilicon film, provided that the process is able to hold the catalyticelements in contact with the surface of the amorphous silicon film, oris able to place them within the amorphous silicon film itself. Forexample, sputtering, CVD, plasma processing, adsorption, ionimplantation, and coating of a solution that contains the catalyticelements can be used. From this group, the process using a solution isuseful in that it is easy to perform, and it is simple to regulate thecatalytic element concentration. Several types of metallic salts can beused, with solvents ranging from water to alcohols, aldehydes, ethers,and other organic solvents. Mixtures of organic solvents and water mayalso be used. A coating method is employed in Embodiment 2. A solutioncontaining between 1 to 1000 ppm nickel (per weight), with a value ofbetween 10 and 100 ppm desirable, is coated. However, depending on thethickness of the amorphous silicon film, it may be necessary to adjustthe concentration by adding a suitable amount of catalyst. An amorphoussilicon film processed in this manner has a nickel concentration ofbetween 1×10¹⁹ and 1×10²¹ atoms/cm³.

After introducing catalytic elements into the amorphous silicon film asdescribed above, crystallization is performed by laser light irradiationin order to obtain a crystallized silicon film. In addition, a hightemperature heating process may be substituted for laser irradiation.Further, a gettering process may be added after crystallization in orderto reduce the concentration of the catalyst in the film.

If further processing is performed according to Embodiment 1, thesemiconductor device of FIG. 1 can be obtained.

Embodiment 3

This embodiment takes an example in which a process that differs fromthat of Embodiment 1 is used to obtain a crystalline semiconductor film.In Embodiment 1, after the heat treatment is given on the base film, asemiconductor film is formed by sputtering, but in Embodiment 3, thebase film and the semiconductor film are formed in succession, withoutexposure to the atmosphere.

First, a plastic substrate is prepared. A silicon nitride film is formedon top of the substrate by sputtering to act as a base film, and anamorphous silicon film is laminated, also by sputtering, to act as asemiconductor film. The two films are formed in succession, withoutexposure to the atmosphere. It is possible to create a clean interfacebetween the base film and the semiconductor film with this processingmethod.

Next, laser light irradiation is used to form a crystallinesemiconductor film by crystallizing the amorphous silicon semiconductorfilm. Further, a gate insulating film may be formed successively bysputtering after the laser process is performed, all without exposure tothe atmosphere, providing a clean interface between the semiconductorfilm and the gate insulating film.

If further processing is performed according to Embodiment 1, thesemiconductor device of FIG. 1 can be obtained. In addition, acombination with Embodiment 2 is possible.

Embodiment 4

A top gate type TFT is used for the explanation of Embodiment 1, howeverthe present invention can also be applied to a bottom gate type TFT,such as an inverted stagger type TFT. In Embodiment 4 of the presentinvention, FIGS. 7A to 7G are used to explain the manufacture of a TFT(bottom gate type TFT) that differs from that of Embodiment 1.

A substrate 700, and a gate wiring 701, that is a laminate of tantalum(Ta) and tantalum nitride (TaN), are shown in FIG. 7A. To simplify thedrawing, the laminate structure of the base film and gate wiring is notshown.

An anodic oxidation process is then performed, forming a protective film702 on the surface of the gate wiring. It is possible to substitute anormal oxidation process for the anodic oxidation process for theoxidized film. Next, a gate insulating film 703 is formed on top of thegate wiring 701. A silicon oxide film formed by sputtering is used asthe gate insulating film 703 in Embodiment 4 (FIG. 7A).

An amorphous silicon film 704 including microcrystalline is then formedby sputtering on top of the gate insulating film 703.

A crystallization process using laser light or heat is next carried out,forming a crystalline semiconductor film 705, as shown in FIG. 7B.

Further, a resist mask 706 is used to form a mask 707 made from asilicon oxide film, as shown in FIG. 7C.

Impurities are then added after removing the resist mask 706, forming animpurity region 708, as shown in FIG. 7D.

Next the area that will become the channel formation region is coveredby a resist mask 709, and a low concentration of impurities is added.This forms a light impurity region 711, a channel formation region 712,and a heavy impurity region 710, as shown in FIG. 7E.

The active layer is patterned next, forming a source region 713 and adrain region 714, as shown in FIG. 7F.

An interlayer insulating film 715 is then formed, as are wirings 716 and717, as shown in FIG. 7G.

Note that Embodiment 4 only contains an explanation of a manufacturingprocess for a single inverted stagger type TFT, but there are nolimitations provided that bottom gate type TFT is made. In addition, byreferring to the manufacturing process outlined in Embodiment 1, it issimple to manufacture CMOS circuits and to form pixel matrix circuitsusing the inverted stagger type TFT of Embodiment 4. Further explanationhas therefore been omitted.

Embodiment 5

An example of a liquid crystal display device manufactured in accordancewith the present invention is shown in FIG. 8. Any well-known means maybe used to manufacture pixel TFTs (pixel switching elements) and groupthem into cells, so an explanation of these processes has been omitted.

A substrate 800 with an insulating surface (a glass substrate with asilicon oxide film), a pixel matrix circuit 801, a scanning line drivecircuit 802, a signal line drive circuit 803, an opposing substrate 830,an FPC 810 (flexible printed circuit), and a logic circuit 820 are allshown in FIG. 8. It is possible to form the logic circuit 820 with acircuit that substitutes existing IC processes, such as those used toform a D/A converter, γ correction circuit, a signal partitioningcircuit, etc. It is of course also possible to put an IC chip on top ofthe substrate, and perform signal processing using the IC chip.

In addition, a liquid crystal display device is given as an example andexplained in Embodiment 5, but it may of course be applied to any activematrix display device such as an EL (electro-luminescence) displaydevice and an EC (electrochromics) display device.

In addition, the present invention may be used to manufacture eithertransmissive type or reflective type liquid crystal display devices. Theoperator is free to choose the type. The present invention is thusapplicable to all active matrix type electro-optical devices(semiconductor devices.)

Note that it is possible to employ any of the previous structures ofEmbodiments 1 through 4, or to freely combine them, in order tomanufacture the semiconductor devices shown in Embodiment 5.

Embodiment 6

This embodiment describes-another example in which a CMOS circuit, thatis a part of a peripheral drive circuit, and a pixel TFT, that is a partof a pixel matrix circuit, are formed on the single same substrate.However, there is difference between this example and Embodiment 1. Thesemiconductor device and its manufacturing method will be describedbriefly with reference to the simple cross sectional drawings shown inFIGS. 9 to 14B.

First a substrate 1100 is prepared. In this embodiment, a glasssubstrate (Corning 1737, distortion point 667° C.) is used as thesubstrate 1100. Next, after a base insulating film 1110 (hereinafter inthis specification, referred to as base film) is formed on top of thesubstrate 1100, it is annealed. The annealing process here is performedbelow the distortion point of the substrate, preferably between 200 and700° C. In Embodiment 6, TEOS and oxygen (O₂) are used as raw materialgasses in a plasma CVD apparatus in order to form a 200 nm thick siliconoxide film as the base film 1110, which is then annealed at 640° C. for4 hours.

A semiconductor film 1150 is then formed on top of the base film 1101 bysputtering. Silicon is used as the target (6 φ) and Ar gas (gas flowrate 20 to 50 sccm) is used as the sputtering gas for Embodiment 6. Inaddition, either hydrogen gas or helium gas may be added (gas flow rate1 to 50 sccm) to regulate the hydrogen density in the semiconductorfilm.

Next, an insulating film 1151 is formed by successively sputtering a 20nm silicon oxide film on top of the semiconductor film 1150, as shown inFIG. 10A. An artificial quartz target is employed in the sputteringprocess, with Ar gas used as the sputtering gas, and oxygen gas used asthe reactive gas, in a ratio of O₂/Ar between 20 and 80%.

After the state shown in FIG. 10A is reached, crystallization of thesemiconductor film 1150 is performed through the insulating film 1151,forming a crystalline semiconductor film 1152 made of a crystallinesilicon film. Laser crystallization of the semiconductor film 1150 isemployed in Embodiment 6. In this embodiment, Excimer laser light isformed into a linear (0.4 mm×length 135 mm) beam and irradiated, underatmospheric conditions (FIG. 10B). The laser beam has a 30 Hz pulsefrequency, an overlap ratio of 96%, and a laser energy density of 175mJ/cm². The surface of the semiconductor film 1150 will not becomecontaminated during laser crystallization processing because theinsulating film 1151 has been formed on the surface of the semiconductorfilm 1150.

After the processing in FIG. 10B is completed, it is acceptable to addimpurities in order to control the threshold value, and to addimpurities in a region to be the channel formation region.

A crystalline semiconductor film 1152 thus obtained and the insulatingfilm 1151 are patterned next, forming active layers 1210, 1300, and1310, and insulating films 1221, 1321, and 1322 (which will become aportion of a gate insulating film after later processing), all indesired shapes, as shown in FIG. 10C.

The active layers 1210, 1300, and 1310, as well as the insulating layers1221, 1321, and 1322, are then covered to form as an insulating film1120 (which will become a portion of the gate insulating film afterfurther processing) a 150 nm thick silicon oxide film deposited bysputtering, as shown in FIG. 10D.

A conductive film (material layer for gate wiring) is then formed on topof the insulating film 1120.

Further, either conductor or semiconductor materials may be used for theconductive film. For example, a single layer containing as its mainconstituent aluminum (Al), tantalum (Ta), copper (Cu), niobium (Nb),hafnium (Hf), zirconium (Zr), titanium (Ti), chromium (Cr), silicon (Si)or silicide may be used, or may be used multi-layers thereof. A filmthickness of 10 to 500 nm can be used for the conductive film. A 400 nmaluminum film is deposited as the conductive film for Embodiment 6.

The conductive film is then patterned using masks 1154 and 1155, and thematerial layers that will form the gate wirings 1156 and 1157 areformed, as shown in FIG. 11A.

In this embodiment, a first anodic oxidation is performed on thematerial layers that will form the gate wirings 1156 and 1157, forminganodic oxidation films 1158 and 1159, which are porous (porous type), asshown in FIG. 11B. Additionally, after removal of the masks 1154 and1155, a second anodic oxidation is performed, forming fine oxidationfilms (barrier type) 1231 and 1331, and then forming gate wirings 1330and 1230, as shown in FIG. 11C.

Additionally, it is also acceptable to add a process that forms aprotective film from an insulating film covering the gate wiring, inorder to protect the gate wiring, without performing the above anodicoxidation.

Next, the gate wirings 1330 and 1230, as well as the anodic oxidationfilms 1158, 1159, 1331, and 1231 are used as a mask, and a highconcentration of impurities that provide n-type conductivity is added inthe active layer, as shown in FIG. 12A. The porous anodic oxidationfilms 1158 and 1159 are then removed, as shown in FIG. 12B. Next, thegate wirings 1330 and 1230, as well as the anodic oxidation films 1331and 1231 are used as a mask, and a low concentration of impurities thatprovide n-type conductivity is added in the active layer, as shown inFIG. 12C. Phosphorous is used as an impurity to provide n-typeconductivity in Embodiment 6.

After the impurity doping process described above is carried out, heavyimpurity regions (n⁺-type regions) 1302, 1303, and 1213 to 1215 act assource and drain regions, while light impurity regions (n⁻-type regions)1304, 1305, and 1216 to 1219 act as LDD regions. Regions not implantedwith either phosphorous or boron ions become intrinsic, or essentiallyintrinsic, channel formation regions 1301, 1211, and 1212, used to routethe carrier.

Next, the n-channel TFT is covered with a mask 1160, and impurities areadded in the active layer to give it p-type conductivity using as a maskthe gate wiring, as shown in FIG. 13A. In addition, it is possible toform a mask that will allow for the selective adding of impurities to apreset area of the active layer. Ion implantation, plasma doping, laserdoping, and other well-known methods may be used as a means for addingimpurities. However, the dose, the acceleration voltage, and otherdoping conditions are regulated in order to ensure that the impurityions are added to preset locations in a desired amount. Boron is used toprovide p-type conductivity in Embodiment 6. After the impurity dopingprocess described above is carried out, heavy impurity regions (p⁺-typeregions) 1312 and 1313 act as source and drain regions, while anintrinsic, or essentially intrinsic, channel formation region 1311 isalso present.

Next, a well-known technique such as thermal annealing or laserannealing is used in order to obtain an activation effect of theimpurities in the source and drain regions, or to get a restorativeeffect for any damage to the active layer crystal structure that wascaused during the doping process. In Embodiment 6, after irradiation bylaser light with a pulse frequency of 50 Hz, and a laser energy densityof 179 mJ/cm², thermal annealing is performed (in a nitrogen atmosphere,405° C., 2 hours.)

Afterward, it is also acceptable to form a passivation film by coveringwith a silicon nitride oxide film, silicon nitride film, etc., in orderto protect the work. In addition, although in Embodiment 6 theinsulating film 1120 is not patterned, it is acceptable to performpatterning of the insulating film 1120 to a desired shape before orafter the impurity adding process. It is also acceptable to selectivelyremove the insulating films 1221, 1321, and 1322 before or after theimpurity adding process.

The mask 1160 is next removed, and then a first interlayer insulatingfilm 1111, a silicon nitride oxide (SiOxNy) film in the Embodiment, isformed, and then after contact holes are formed to expose the source anddrain regions, a metallic film is formed. This metallic film ispatterned, forming metallic wirings 1341 to 1343, 1240, and 1241 thatprovide contact with the source and drain regions. Finally this ishydrogenated in a hydrogen atmosphere at 350° C. for 2 hours (FIG. 13B).

The n-channel TFT and p-channel TFT are manufactured by performing theseprocesses.

Next, a second interlayer insulating film 1112 is formed by spin coatingan acrylic resin to a thickness of 1 μm. The second interlayerinsulating film 1112 is then etched, and after contact holes are formed,a 300 nm Ti metallic film is deposited. After then patterning themetallic film, a black mask 1250 and lead wires 1351 and 1352 areformed.

Next, a third interlayer insulating film 1113 is formed by an acrylicresin. In Embodiment 6 the third interlayer insulating film 1113 isformed by spin coating to a thickness of 3 μm.

A contact hole is then formed, and a pixel electrode 1260 is formed. InEmbodiment 6, first a transparent conductive film, for example, an ITOfilm is sputtered to a thickness of 100 nm, and then it is patterned,forming the pixel electrode 1260. As a pixel electrode, a compoundcomprising indium oxide and zinc oxide can be also used instead of ITO.Finally, this is treated with heat for 1 hour at 350° C. in a hydrogenatmosphere, reducing defects throughout the semiconductor layers. Theconditions shown in FIG. 9 are thus obtained.

Although in FIG. 9 a double gate structure pixel matrix TFT is used forthe explanation, the present invention may also be applied to singlegate, triple gate, and other multiple gate structures.

FIGS. 14A and 14B are equivalent to top views of the drawing shown inFIG. 9. The portion cut along the dotted line X-X′ corresponds to thecross sectional view of the pixel matrix circuit construction in FIG. 9,while the portion cut along the dotted line Y-Y′ corresponds to thecross sectional view of the CMOS circuit construction. An active layer1210, a scanning line 1220, a gate wiring 1230E, a signal line 1240, adrain electrode 1241, a black mask 1250, and a pixel electrode 1260 areall shown in FIG. 14A. In FIG. 14B, active layers 1300 and 1310, a gatewiring 1330, a drain wiring 1335, source electrodes 1341 and 1342, adrain electrode 1343, and source wirings 1351 and 1352 are shown.

The TFT structure shown in Embodiment 6 is an example of a top gatetype, and places no special limitations on the structure of Embodiment6. In addition, Embodiment 6 shows the manufacture of a transmissiveLCD, which is just one example of a semiconductor device. Note that byconstructing the pixel electrode with a highly reflective metal film,instead of ITO, and then suitably changing the patterning of the pixelelectrode, the operator can easily manufacture a reflective LCD. Inaddition, by using as a base film a structure consisting of a heatresistant metal film and an insulating film layered thereon, or astructure comprising an insulating film formed on top of aluminumnitride during manufacture of the reflective LCD, the metallic filmunderneath the insulating film will work effectively as a heat radiationlayer. Also note that operators may suitably change the order of theabove processes as needed.

It is possible to combine Embodiment 6 with Embodiment 5.

Embodiment 7

This embodiment takes an example in which a process that differs fromthat of Embodiment 6 is used to obtain a crystalline semiconductor film.In Embodiment 7 an additional process is performed before formation ofthe semiconductor film of Embodiment 6, which places a catalytic elementeither selectively or over the entire semiconductor surface, in order topromote crystallization. The basic structure of Embodiment 7 is similarto that of Embodiment 1, therefore the focus of the description will beon the differences only.

A catalytic element to promote silicon crystallization is added to thesemiconductor film bottom surface in Embodiment 7. Elements Ni, Fe, Co,Pt, Cu, Au, and Ge may be used either singly, or in combination, as thecatalytic element for promoting silicon crystallization. Ni was chosenfrom those catalytic elements for Embodiment 7 due to its quickdiffusion speed throughout the amorphous silicon film, and the extremelygood crystallinity was obtained.

In addition, there are no special limitations on what location the abovecatalytic element may be introduced. It is added either over the entirebase film surface, or added to selective areas through use of a suitablemask.

Further, there are no special limitations on what type of processingmethod is used to introduce the catalytic element to the amorphoussilicon film, provided that the process is able to place the catalyticelements in contact with the bottom surface of the amorphous siliconfilm, or is able to hold them within the amorphous silicon film itself.For example, sputtering, CVD, plasma processing, adsorption, ionimplantation, and coating with a solution that contains the catalyticelements can be used. From this group, the process using a solution isuseful in that it is easy to perform, and it is simple to regulate thecatalytic element concentration. Several types of metallic salts can beused, with solvents ranging from water to alcohols, aldehydes, ethers,and other organic solvents. Mixtures of organic solvents and water mayalso be used. A coating method is employed in this embodiment. Asolution containing between 1 to 1000 ppm nickel (per weight), with avalue of between 10 and 100 ppm desirable, is coated. However, dependingon the thickness of the amorphous silicon film, it may be necessary toadjust the concentration by adding a suitable amount of catalyst. Anamorphous silicon film processed in this manner has a concentration ofbetween 1×10¹⁹ and 1×10²¹ atoms/cm³.

After introducing catalytic elements into the amorphous silicon film asdescribed, an insulating layer is formed without exposure to theatmosphere, and crystallization is performed through the insulatinglayer by laser light irradiation in order to obtain a crystallizedsilicon film. In addition, a high temperature heating process may besubstituted for laser irradiation. Further, a gettering process may beadded after crystallization in order to reduce the concentration of thecatalytic element in the film.

If further processing is performed according to Embodiment 6, thesemiconductor device of FIG. 9 can be obtained.

Embodiment 8

This embodiment takes an example in which a process that differs fromthat of Embodiment 6 is used to obtain a crystalline semiconductor film.In Embodiment 6, after heat treatment is given on the base film, asemiconductor film is formed by sputtering, but in Embodiment 8, thebase film, the semiconductor film and the insulating film are formed insuccession, without exposure to the atmosphere.

First, a plastic substrate is prepared. A silicon nitride film is formedon top of the substrate by sputtering to act as a base film, and anamorphous silicon film is laminated, also by sputtering, to act as asemiconductor film. The two films are formed in succession, withoutexposure to the atmosphere. It is possible to create a clean interfacebetween the base film and the semiconductor film with this processingmethod. In addition, sputtering is used to successively form a 20 nminsulating film of silicon oxide, without exposure to the atmosphere.This can provide a clean interface between the semiconductor film andthe insulating film.

Next, laser light irradiation is used to form a crystallinesemiconductor film by crystallizing the amorphous silicon semiconductorfilm through the insulating film.

If further processing is performed according to Embodiment 6, thesemiconductor device of FIG. 9 can be obtained.

Embodiment 9

This embodiment takes an example in which a multi-chamber (cluster tool)structured apparatus such as the one shown in FIGS. 17A and 17B is usedto form the laminates of films formed by sputtering in Embodiments 1 to3, and 6 to 8.

In Embodiment 9, a silicon oxide film is formed as a base film in afirst chamber 19, fitted with a fused quartz target, at a depositionpressure of 0.6 Pa, and using a sputtering gas comprised of a 0 to 50%mixture ratio of O₂ and Ar gasses. A 30% mixture ratio is used here.

Next, without exposure to the atmosphere, the substrate is conveyed to asecond chamber 20, fitted with a silicon target, in which Ar gas is usedas the sputtering gas in order to form a semiconductor film of amorphoussilicon.

Then, without exposure to the atmosphere, the substrate is conveyed to athird chamber 21, fitted with a fused quartz target. An insulating filmmade from silicon oxide is formed in the third chamber 21, at adeposition pressure of 0.6 Pa, and using a sputtering gas comprised of a20 to 80% mixture ratio of O₂ and Ar gasses. A 30% mixture ratio is usedin here.

It is desirable that a well-known cleaning process be carried-out on thesurface on which the film is to be formed before forming the film in thesputtering process.

Next, the semiconductor film, made of an amorphous silicon film, iscrystallized by laser light irradiation through the insulating film,forming a crystalline semiconductor film.

If further processing is performed according to Embodiment 6, thesemiconductor device of FIG. 9 can be obtained.

Embodiment 10

A top gate type TFT is used for the explanation of Embodiment 6, howeverthe present invention can also be applied to a bottom gate type TFT,such as an inverted stagger type TFT. In Embodiment 10, FIGS. 15A to 15Dand FIGS. 16A to 16C are used to explain the manufacture of a TFT(bottom gate type TFT) that differs from that of Embodiment 6.

A substrate 1500, and a gate wiring 1501 consisting of a laminate oftantalum (Ta) and tantalum nitride (TaN), are shown in FIG. 15A. Tosimplify the drawing, the laminate structure of the base film and gatewiring is not shown.

An anodic oxidation process is then performed, forming a protective film1502 on the surface of the gate wiring. It is also possible tosubstitute an oxide film by a normal oxidation process for the anodicoxidation film by the anodic oxidation process. Next, a gate insulatingfilm 1504 is formed on top of the gate wiring 1501. A silicon oxide filmformed by sputtering is used as the gate insulating film 1504 forEmbodiment 10.

Then, without exposure to the atmosphere, an amorphous silicon film 1505including microcrystalline is formed by sputtering on top of the gateinsulating film 1504, and on top of this an insulating film 1503, madefrom a silicon nitride film, is also formed, as shown in FIG. 15A.

A crystallization process using laser light or heat is next carried outthrough the insulating film 1503, forming a crystalline semiconductorfilm 1506, as shown in FIG. 15B.

Next, a resist mask 1507 is used to form a mask 1508 made from a siliconoxide film, as shown in FIG. 15C.

Impurities are then added after removing the resist mask 1507, formingimpurity regions 1509 and 1510, as shown in FIG. 15D.

Next, the area that will become the channel formation region is coveredby a resist mask 1511, and a low concentration of impurities is added.This forms light impurity regions 1524 and 1525, a channel formationregion 1521, and heavy impurity regions 1522 and 1523, as shown in FIG.16A.

It is also acceptable to remove the insulating film 1503 either beforeor after the adding the impurity.

The active layer is patterned next, forming a source region 1532 and adrain region 1533, as shown in FIG. 16B.

An interlayer insulating film 1540 is formed next, as are wirings 1541and 1542, as shown in FIG. 16C.

Note that Embodiment 10 only contains an explanation of a manufacturingprocess for a single inverted stagger type TFT. However, by referring tothe manufacturing process outlined in Embodiment 6, it is simple tomanufacture CMOS circuits and to form pixel matrix circuits using theinverted stagger type TFT of Embodiment 10. Further explanation hastherefore been omitted.

Embodiment 11

The present invention can generally be applied to all previous andcurrent IC technologies. Namely, it is applicable to all semiconductorcircuits currently on the market. For example, it is applicable tomicroprocessors like integrated circuit RISC and ASIC processors, tosignal processing circuits like those used as driver circuits for liquidcrystals (a D/A converter, a γ correction circuit, a signal partitioningcircuit, etc.), and to high frequency circuits such as those found inportable equipment (cellular phones, PHS phones, mobile computers).

In addition, semiconductor circuits like microprocessors are loaded intoa wide array of electronic equipment and function as the nucleus of suchequipment. Representative examples of electronic equipment includepersonal computers, portable information terminals, etc., namely allhome electronic products. Further, computers that control vehicles(automobiles, trains, etc.) can also be given as examples. The presentinvention can be applied to this wide array of semiconductor devices.

It is possible to employ any of the previous structures of Embodiments 1through 10, or to freely combine them, in order to manufacture thesemiconductor devices shown in this embodiment.

Embodiment 12

A TFT formed through carrying out the present invention may be appliedto various electro-optical devices. Namely, the present invention may beembodied in all the electronic equipments that incorporate thoseelectro-optical devices as display media.

As such an electronic equipment, a video camera, a digital camera, ahead-mount display (goggle-type display), a wearable display, anavigation system for vehicles, a personal computer, and a portableinformation terminal (a mobile computer, a cellular phone, or anelectronic book) may be enumerated. Examples of those are shown in FIGS.18A to 18H.

FIG. 18A shows a personal computer comprising a main body 2001, an imageinputting unit 2002, a display device 2003, and a key board 2004. Thepresent invention is applicable to the image inputting unit 2002, thedisplay device 2003, and other signal control circuits.

FIG. 18B shows a video camera comprising a main body 2101, a displaydevice 2102, a voice input unit 2103, operation switches 2104, a battery2105, and an image receiving unit 2106. The present invention isapplicable to the display device 2102, the voice input unit 2103, andother signal control circuits.

FIG. 18C shows a mobile computer comprising a main body 2201, a cameraunit 2202, an image receiving unit 2203, an operation switch 2204, and adisplay device 2205. The present invention is applicable to the displaydevice 2205 and other signal control circuits.

FIG. 18D shows a goggle-type display comprising a main body 2301,display devices 2302 and arm portions 2303. The present invention isapplicable to the display devices 2302 and other signal controlcircuits.

FIG. 18E shows a player that employs a recording medium in whichprograms are recorded (hereinafter referred to as recording medium), andcomprises a main body 2401, a display device 2402, a speaker unit 2403,a recording medium 2404, and an operation switch 2405. Incidentally,this player uses as the recording medium a DVD (digital versatile disc),a CD and the like to serve as a tool for enjoying music or movies, forplaying video games and for connecting to the Internet. The presentinvention is applicable to the display device 2402 and other signalcontrol circuits.

FIG. 18F shows a digital camera comprising a main body 2501, a displaydevice 2502, an eye piece section 2503, operation switches 2504, and animage receiving unit (not shown). The present invention is applicable tothe display device 2502 and other signal control circuits.

FIG. 18G shows a cellular phone comprising a main body 2601, a voiceoutput portion 2602, a voice input portion 2603, a display device 2604,operation switches 2605, and an antenna 2606.

FIG. 18H shows a portable book (an electronic book) comprising a mainbody 2701, display devices 2702 and 2703, a recording medium 2704,operation switches 2705, and an antenna 2706.

As described above, the present invention has so wide application rangethat it is applicable to electronic equipments in any fields. Inaddition, the electronic equipment of this embodiment may be realizedwith any construction obtained by combining Embodiments 1 to 11.

Embodiment 13

A TFT formed through carrying out the present invention may be appliedto various electro-optical devices. Namely, the present invention may beembodied in all the electronic equipments that incorporate thoseelectro-optical devices as display media.

As such an electronic equipment, projectors (rear-type projector orfront-type projector) are exemplified. Examples of those are shown inFIGS. 19A to 19D.

FIG. 19A shows a front-type projector comprising a display device 3001and a screen 3002. The present invention is applicable to the displaydevice and other signal control circuits.

FIG. 19B shows a rear-type projector comprising a main body 3101, adisplay device 3102, a mirror 3103, and a screen 3104. The presentinvention is applicable to the display device and other signal controlcircuits.

FIG. 19C is a diagram showing an example of the structure of the displaydevices 3001 and 3102 in FIGS. 19A and 19B. The display device 3001 or3102 comprises a light source optical system 3201, mirrors 3202 and 3204to 3206, dichroic mirrors 3203, a prism 3207, liquid crystal displaydevices 3208, phase difference plates 3209, and a projection opticalsystem 3210. The projection optical system 3210 is comprised of anoptical system including a projection lens. This embodiment shows anexample of “three plate type”, but not particularly limited thereto. Forinstance, the invention may be applied also to “single plate type”.Further, in the light path indicated by an arrow in FIG. 19C, an opticalsystem such as an optical lens, a film having a polarization function, afilm for adjusting a phase difference, an IR film may be suitablyprovided by a person who carries out the invention.

FIG. 19D is a diagram showing an example of the structure of the lightsource optical system 3201 in FIG. 19C. In this embodiment, the lightsource optical system 3201 comprises a reflector 3211, a light source3212, lens arrays 3213 and 3214, a polarization conversion element 3215,and a condenser lens 3216. The light source optical system shown in FIG.19D is merely an example thereof, and is not particularly limited. Forinstance, on discretion of a person who carries out the invention, thelight source optical system may be provided with an optical system suchas an optical lens, a film having a polarization function, a film foradjusting the phase difference, and an IR film.

As described above, the present invention has so wide application rangethat it is applicable to electronic equipments in any fields. Inaddition, the electronic equipment of this embodiment may be realizedwith any construction obtained by combining Embodiments 1 to 10.However, though mentioning this would be unnecessary, the projectors inthis embodiment are transmissive liquid crystal display devices andhence cannot be applied to reflective liquid crystal display devices.

When manufacturing the semiconductor devices shown in this embodiment,any construction in Embodiments 1 through 10 may be adopted, andEmbodiments may be freely combined. Also, the electro-optical devicesand the semiconductor circuits may be used in combination.

Embodiment 14

This example demonstrates a process for producing an EL(electroluminescence) display device according to the invention of thepresent application.

FIG. 20A is a top view showing an EL display device which was producedaccording to Embodiments 1-4 and 6-10 of the present invention. In FIG.20A, there are shown a substrate 4010, a pixel portion 4011, a sourceside driving circuit 4012, and a gate side driving circuit 4013, eachdriving circuit connecting to wirings 4014-4016 which reach FPC 4017leading to external equipment.

The pixel portion, preferably together with the driving circuits, isenclosed by a sealing material (or a housing material) 4018. The sealingmaterial 4018 may be a concave metal plate or glass plate which enclosesthe element; alternatively, it may be an ultraviolet curable resin. Whena metal plate having a concave portion to enclose the element isemployed as the sealing material, the concave metal plate should befixed to the substrate 4010 with an adhesive 4019 so that an airtightspace is formed between the metal plate and the substrate 4010. Thus,the EL element is completely sealed in the airtight space and completelyisolated from the outside air.

It is desirable that the cavity 4020 between the sealing material 4018and the substrate 4010 be filled with an inert gas (such as argon,helium, and nitrogen) or a desiccant (such as barium oxide), so as toprotect the EL element from degradation by moisture.

FIG. 20B is a sectional view showing the structure of the EL displaydevice in this Embodiment. There is shown a substrate 4010, a base film4021, a TFT 4022 for the driving circuit, and a TFT 4023 for the pixelportion. (The TFT 4022 shown is a CMOS circuit consisting of ann-channel type TFT and a p-channel type TFT. The TFT 4023 shown is theone which controls current to the EL element.) Needless to say, each ofthese TFTs may have a top gate structure shown in Embodiments 1-3 and6-8 or a bottom gate structure shown in Embodiments 4 and 10.

The present invention may be employed to form the semiconductor layerwhich becomes the active layer 4024 of TFT 4022 for the driving circuitand the active layer 4025 of TFT 4023 for the pixel portion.

Upon completion of TFT 4022 for the driving circuit and TFT 4023 for thepixel portion, with their active layer being the semiconductor layerformed according to the present invention, a pixel electrode 4027 isformed on the interlayer insulating film (a leveling film) 4026 made ofa resin. This pixel electrode is a transparent conductive film which iselectrically connected to the drain of TFT 4023 for the pixel portion.The transparent conductive film may be formed from a compound (calledITO) of indium oxide and tin oxide or a compound of indium oxide andzinc oxide. On the pixel electrode 4027 is formed an insulating film4028, in which is formed an opening above the pixel electrode 4027.

Subsequently, the EL layer 4029 is formed. It may be of single-layerstructure or multi-layer structure by freely combining known ELmaterials such as a hole injection layer, a hole transport layer, alight emitting layer, an electron transport layer, and an electroninjection layer. Any known technology may be available for suchstructure. The EL material is either a low-molecular material or ahigh-molecular material (polymer). When the low-molecular material isused, a vapor deposition can be applied, and when the high molecularmaterial (polymer) is used, a simple method such as spin coating,printing, or ink-jet method can be applied.

In this Embodiment, the EL layer is formed by vapor deposition through ashadow mask. The resulting EL layer permits each pixel to emit lightdiffering in wavelength (red, green, and blue). Thus, this realizes thecolor display. Alternative systems available include the combination ofa color conversion layer (CCM) and a color filter and the combination ofwhite light emitting layer and color filter. Needless to say, the ELdisplay device may be monochromatic.

On the EL layer 4029 is formed a cathode 4030. Prior to this step, it isdesirable to clear moisture and oxygen as much as possible from theinterface between the EL layer 4029 and the cathode 4030. This objectmay be achieved by forming the EL layer 4029 and the cathode 4030consecutively in a vacuum, or by forming the EL layer 4029 in an inertatmosphere and then forming the cathode 4030 in the same atmospherewithout exposure to air. In this Embodiment, the desired film was formedby using a film-forming apparatus of a multi-chamber system (a clustertool system).

The multi-layer structure composed of a lithium fluoride film and analuminum film is used in this Embodiment as the cathode 4030. To beconcrete, the EL layer 4029 is coated by vapor deposition with a lithiumfluoride film (1 nm thick) and an aluminum film (300 nm thick)sequentially thereon. Needless to say, the cathode 4030 may be formedfrom MgAg electrode which is a known cathode material. Subsequently, thecathode 4030 is connected to a wiring 4016 in the region indicated by4031. The wiring 4016 to supply a prescribed voltage to the cathode 4030is connected to the FPC 4017 through an electrically conductive pastematerial 4032.

The electrical connection between the cathode 4030 and the wiring 4016in the region 4031 needs contact holes in the interlayer insulating film4026 and the insulating film 4028. These contact holes may be formedwhen the interlayer insulating film 4026 undergoes etching to form thecontact hole for the pixel electrode or when the insulating film 4028undergoes etching to form the opening before the EL layer is formed.When the insulating film 4028 undergoes etching, the interlayerinsulating film 4026 may be etched simultaneously. Contact holes of goodshape may be formed if the interlayer insulating film 4026 and theinsulating film 4028 are made of the same material.

The wiring 4016 is electrically connected to FPC 4017 through the gap(filled with an adhesive 4019) between the sealing material 4018 and thesubstrate 4010. As in the wiring 4016 explained above, other wirings4014 and 4015 are also electrically connected to FPC 4017 under thesealing material 4018.

The above-mentioned EL display device constructed according to thepresent invention is advantageous in that the semiconductor film used asan active layer of a TFT can have high electrical characteristics.Therefore, the EL display comprising TFTs which has been produced withaccordance to the present invention can produce display images of goodquality.

According to the present invention, an amorphous silicon film is formedby the sputtering process, which enables a TFT to be manufactured in ahighly safe work environment. It is also easy to regulate the filmquality with sputtering, enabling an amorphous semiconductor film to beformed as desired.

In addition, films formed by sputtering have good adhesion, so it ispossible to form an extremely high quality crystallized film, withinterface of good adhesion, even when a low cost plastic or glasssubstrate is used. It is thus possible to use the present invention tomanufacture a high performance semiconductor device.

Further, it is possible to obtain a semiconductor device with goodelectrical characteristics when using the present invention due to theclean interface that can be obtained between, especially, the channelformation region of the active layer and the insulating layer formedthereon.

Additionally, a TFT fabricated through the present invention has themobility (μ_(max)), which is the representative parameter for TFTs,between 50 to 500 cm²/Vs (100 cm²/Vs or more) for an n-channel type TFT,and between 20 to 300 cm²/Vs (50 cm²/Vs or more) for a p-channel typeTFT.

1. A semiconductor device comprising: a first substrate; an insulatingfilm over the first substrate; a pixel electrode formed over theinsulating film; an EL layer formed over the pixel electrode; a secondelectrode formed over the EL layer, and electrically connected to awiring formed on the insulating film; and a second substrate having afirst region with a first thickness, covering the insulating film, thepixel electrode, the EL layer and the second electrode, and a secondregion with a second thickness, fixed to the first substrate by anadhesive and the adhesive is directly in contact with the wiring on theinsulating film, wherein the first region is inside the second regionand the first region is depressed relative to the second region.
 2. Thesemiconductor device according to claim 1, wherein a thin filmtransistor is formed over the insulating film, and electricallyconnected to the pixel electrode.
 3. The semiconductor device accordingto claim 1, wherein a cavity between the first substrate and the firstregion is filled with an inert gas.
 4. The semiconductor deviceaccording to claim 1, wherein a desiccant is contained in a cavitybetween the first substrate and the first region.
 5. The semiconductordevice according to claim 1, wherein the wiring is connected to an FPCthrough an electrically conductive paste material.
 6. A semiconductordevice comprising: a first substrate; an insulating film over the firstsubstrate; a pixel electrode formed over the insulating film; an ELlayer formed over the pixel electrode; a second electrode formed overthe EL layer, and electrically connected to a wiring formed on theinsulating film; and a second substrate having a first region with afirst thickness, covering the insulating film, the pixel electrode, theEL layer and the second electrode, and a second region with a secondthickness, fixed to the first substrate by an adhesive and the adhesiveis directly in contact with the wiring on the insulating film, whereinthe first region is inside the second region and the first region isdepressed relative to the second region, and wherein the first substrateis a glass substrate.
 7. The semiconductor device according to claim 6,wherein a thin film transistor is formed over the insulating film, andelectrically connected to the pixel electrode.
 8. The semiconductordevice according to claim 6, wherein a cavity between the firstsubstrate and the first region is filled with an inert gas.
 9. Thesemiconductor device according to claim 6, wherein a desiccant iscontained in a cavity between the first substrate and the first region.10. The semiconductor device according to claim 6, wherein the wiring isconnected to an FPC through an electrically conductive paste material.11. A semiconductor device comprising: a first substrate; an insulatingfilm over the first substrate; a pixel electrode formed over theinsulating film; an EL layer formed over the pixel electrode; a secondelectrode formed over the EL layer, and electrically connected to awiring formed on the insulating film; and a second substrate having afirst region with a first thickness, covering the insulating film, thepixel electrode, the EL layer and the second electrode, and a secondregion with a second thickness, fixed to the first substrate by anadhesive and the adhesive is directly in contact with the wiring on theinsulating film, wherein the first region is inside the second regionand the first region is depressed relative to the second region, andwherein the second substrate is a glass substrate.
 12. The semiconductordevice according to claim 11, wherein a thin film transistor is formedover the insulating film, and electrically connected to the pixelelectrode.
 13. The semiconductor device according to claim 11, wherein acavity between the first substrate and the first region is filled withan inert gas.
 14. The semiconductor device according to claim 11,wherein a desiccant is contained in a cavity between the first substrateand the first region.
 15. The semiconductor device according to claim11, wherein the wiring is connected to an FPC through an electricallyconductive paste material.
 16. A semiconductor device comprising: afirst substrate; an insulating film over the first substrate; a pixelelectrode formed over the insulating film; an EL layer formed over thepixel electrode; a second electrode formed over the EL layer, andelectrically connected to a wiring formed on the insulating film; and asecond substrate having a first region with a first thickness, coveringthe insulating film, the pixel electrode, the EL layer and the secondelectrode, and a second region with a second thickness, fixed to thefirst substrate by an adhesive and the adhesive is directly in contactwith the wiring on the insulating film, wherein the first region isinside the second region and the first region is depressed relative tothe second region, wherein the first substrate is a glass substrate, andwherein the second substrate is a glass substrate.
 17. The semiconductordevice according to claim 16, wherein a thin film transistor is formedover the insulating film, and electrically connected to the pixelelectrode.
 18. The semiconductor device according to claim 16, wherein acavity between the first substrate and the first region is filled withan inert gas.
 19. The semiconductor device according to claim 16,wherein a desiccant is contained in a cavity between the first substrateand the first region.
 20. The semiconductor device according to claim16, wherein the wiring is connected to an FPC through an electricallyconductive paste material.